Changing consumer unit - testing etc

[Ben Blaukopf]

a) I'm looking at buying the SpeedTest2018 from

which I think does everything I need in order to fill in a BS7671 design and install cert. It's 215 quid, but can't find anyone who has used it on google. Does it seem reasonable, and is it missing anything? It does RCD disconnects and earth fault loop, which I

b) My existing CU (crowded 6-way fusebox with fusewire) is running both a ring and a radial circuit both with 2.5mm wire from the same way. Surely this can't be OK, because the radial circuit isn't protected by the 30A fuse?

c) Is it legal to move the meter board, and anything I should know before doing it? I've got sufficient flex in the incomers to do this, and I only need to shift it sideways a fraction - I've got a 32cm gap for the CU next to it, and need a couple of cm more to fit most 12 way CUs.

d) Is running two equivalently rated circuits on a suitable MCB OK? e.g.

16A MCB with two radial circuits, one for the immersion heater, and one powering a 13A socket for the fridge-freezer? Or do I have to do a diversity calculation before I can do this? I might need to do this if the answer to c) is no!

e) When I change the CU, I will then have 2 lights circuits, immersion heater, cooker, 2 rings, garage, shed, cooker. Is there any possibility that the BCO will then moan that the 60A company fuse is inadequate and I need to get them to improve the supply?

f) Ditto e) but I then want to add an underfloor heating circuit.

Thanks!

Ben

[Andy Wade]

It doesn't appear to do insulation resistance and continuity/low-ohms, both of which are must-haves.

It's OK if the 'radial' can be regarded as a spur off the ring, i.e. it feeds only one single or one double socket, or one item of fixed equipment.

Strictly speaking no, but for such a small amount... What type of service cable have you got? Be very careful indeed if it's an old paper or jute insulated (lead sheathed) cable as these can be quite fragile.

One MCB means it would be one final circuit feeding two points, not two circuits. Don't do it! - use of such unconventional circuit arrangements is strongly discouraged, even if they do comply with BS 7671.

Did you really mean two cookers? Assuming not, I answer "unlikely."

Now we're into "possibly" - but what underfloor heating load do you envisage?

[meow2222]

It would all work ok, but if somethng of higher power is plugged into the socket later, you'd likely get nuisance trips.

Also immersion heaters do go pop sooner or later, so it would end up costing you more in lost food than you'd save by skimping.

only if youre using a whole lot of UFH. And there are ways round that if required.

NT

[Christian McArdle]

It appears to be a loop tester and RCD tester. You will also need a compliant insulation/continuity tester.

No, it is perfectly OK, although I would normally avoid it as (a) it confuses and (b) there's enough cable inside a consumer unit already. Unless you're saying the spur cable is off the SUPPLY side of the MCB...

Technically no you may not move it. Of course, unless you're a muppet and short something out, they'll never find out.

Whilst electrically OK, such a combination is inappropriate, as you should either make entirely general purpose socket circuits, or single purpose easily described fixed circuits. For example, sharing an immersion and central heating is OK, as you can describe it as the "heating" system. Sharing a freezer and an immersion is bizarre. If you can't make a good job of describing the circuit with one word, then think again.

need to do this if

I'd say that it easily passes diversity for the fixed appliances. The freezer won't consume anything like the 3A left over in normal usage, maybe peak above for a second or two when the compressor fires up, but nothing to worry about. The reason I would not use this circuit combination is that it is unusual and might result in isolation misunderstandings.

No. If they do, they'll probably upgrade you to 100A for free. If you also have an electric shower (as well as a presumably electric cooker), then ask them yourself and until they replace it, don't cook the Christmas dinner whilst having a long shower.

Christian.

[Ben Blaukopf]

In which case the price goes up to 349 for

to chat to the BCO in a minute to find out whether I can balance his inspection requirements with not having the power off for too long...

No! OK, I understand it can be treated as a spur. I still want to get rid of it in the new one though.

Got it.

I'm having enough trouble figuring out my existing circuitry (which has the downstairs extension lit from the upstairs lights circuits, among other things), so am keen to end up with something simple for the next guy to look at it.

Great. It's only a theoretical problem at the moment, since the cooker will be dual fuel, and most likely 13A oven, and I have NO intention of putting an electric shower in. But I don't want to make life too difficult for a subsequent owner if they want an electric hob...

Ben

[Christian McArdle]

60A will be more than sufficient. Ask them for 100A if they'll do it for free if you like, though.

That's where we differ. I like to make it as hard as possible to fit those abominations.

Christian.